Hey guys just wanted to add my 2cents worth, I purchased a full exhaust from mat at magic performance which includes one of these cats, I am extremely happy with the results. My 32 makes 142kw at the rear wheels with an air filter and one of magics exhaust systems. SO you can see thats about a 30 kw gain from your average stock gtst.
Also mat made me up a straight pipe to replace the cat when i go to the track and i hardly notice any difference(if any) when that is in instead of the cat so it must be flowing pretty good. The only thing you have to watch is if you go to the track without replacing the cat with a straight pipe you can overheat the cat, although this is the same with all metalic substraight cats like the catco.
Hope this helps